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Possible Scout main jet sizes.

Moderators: Curt!, Pa

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dirtyss

Posts: 16

Joined: Sat Feb 27, 2010 8:05 am

Post Sun Feb 28, 2010 7:51 am

Possible Scout main jet sizes.

Hi, my first post on this great site, probably going in at the deep end here.
I'm fairly new to indians though I've wanted one for many years, so I recently picked up a nicely bobbed 741. The motor has been stroked to around 50 cu in and the bike generally has been put together with alot of nice period touches. I'm currently sorting all those fiddly troublesome bits that can get overlooked on a total rebuild sometimes.
My bike is fitted with a M51 Harley carb, externally vented, with plugged main jet and a 4 hole main nozzle, this, needless to say is a fair way off from the M633-642 Indian spec carb, the bike runs extemely rich after idle, through transition, cruise to main mixture.
With the help of the really useful "Linkert book" I have been better able to understand how the carburettor works and note the differences in the setups of Indian carbs to Harley carbs. So I have purchased a scout 45 main nozzle with 5 holes and other linkert rebuild parts to start correcting the fuelling problems. Has anybody used harley main jets in their Indians ? if so, is there a size to start from ?

Many thanks, best regards
Paul
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Pa

Site Admin

Posts: 4751

Joined: Sun Mar 12, 2000 1:01 am

Location: Ohio USA

Post Sun Feb 28, 2010 8:09 am

Re: Possible Scout main jet sizes.

Welcome aboard Paul. Pa
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panic

Post Sun Feb 28, 2010 9:39 am

Re: Possible Scout main jet sizes.

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Last edited by panic on Sun Nov 28, 2010 6:13 pm, edited 1 time in total.
<<

dirtyss

Posts: 16

Joined: Sat Feb 27, 2010 8:05 am

Post Fri Mar 12, 2010 4:35 am

Re: Possible Scout main jet sizes.

Thanks for the welcome Pa.

Panic - my motor is: 741 crankcases, Scout jugs and pistons, harley 45 flywheels = 49.43 cu in. She may have a bit of wear in those bores now, so I like to call it 50 cu in :D

I was confused with the paragraph within the linkert book
"Conversely, if the engine runs best with the needle out more than four turns, increasing the main jet size (if a sized jet is present) or adding a jet( if only a plug is present) is indicated"
I got half turns confused with full turns (thats how I count the turns) and at 5 half turns (2.5 turns) to run correctly I thought I needed to think about fitting a jet - panic over (sorry for pun)

Thanks. best regards

Paul
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Cotten

User avatar

Posts: 2680

Joined: Thu Sep 30, 1999 12:01 am

Location: Central Illinois, USA

Post Sun Mar 14, 2010 7:50 am

Re: Possible Scout main jet sizes.

Paul!

The most common reason for running rich is that it won't run any leaner.

Have you pressuretested for vacuum leaks?

....Cotten
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dirtyss

Posts: 16

Joined: Sat Feb 27, 2010 8:05 am

Post Tue Apr 27, 2010 4:31 am

Re: Possible Scout main jet sizes.

Cotten wrote:Paul!

The most common reason for running rich is that it won't run any leaner.

Have you pressuretested for vacuum leaks?

....Cotten



Hi Cotten
You are right about that, however, I have thoroughly tested for leaks and there are none.

So.....
Having set the float to the "brass level" of 3/8" (1/4" was way too rich), replaced the thottle shaft and bushes and changed the emulsion tube / jet to a 5 hole Indian Scout one. I now have a bike that runs very evenly and smoothly at tick over and will snap open and rev cleanly out of gear. Will run smooth up to approx 1200/1300 rpm in all gears, but if I open throttle for power she two stokes or misses. The bike still smells as if shes too rich - should I try lowering the fuel level some more or concerntrate on the power needle adjustment - which incidently half a tun can stop the bike. The idle mixture screw seems to be quite sensitive as well, one more click whist running smoothly can stop the engine.
I managed a 14 mile round trip with no break down the other day, loved every minute of it, be nice to sort this carb out soon.

Regards
Paul
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panic

Post Tue Apr 27, 2010 7:49 am

Re: Possible Scout main jet sizes.

Are you sure this isn't an electrical misfire (plug gap, coil voltage, condenser)?
<<

dirtyss

Posts: 16

Joined: Sat Feb 27, 2010 8:05 am

Post Thu Apr 29, 2010 3:00 am

Re: Possible Scout main jet sizes.

Good point Panic - I was about to check the plugs this weekend, I can subsitute most parts except for the coil.

regards
Paul
<<

dirtyss

Posts: 16

Joined: Sat Feb 27, 2010 8:05 am

Post Fri May 07, 2010 6:45 am

Re: Possible Scout main jet sizes.

Ok
Changed plugs and condenser for new, double checked points, timing and spark strength - alls well. As she was running very rich still I took carb off and reset the fuel level from 3/8" to 7/16". Road test got power needle turned in half a turn and she pulls like a train revving nice and cleanly - at last !

Now at running temperature she is idling way too fast 8 -900 rpm and the throttle disc is shut completely ! I cannot see how I can adjust this out with the idle screw only. I can get a good even low tick over when she is cold and warming up - probably too rich at idle now ?

Regards
Paul
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jib

Posts: 573

Joined: Sat Dec 10, 2005 3:36 pm

Location: devon,england

Post Fri May 07, 2010 9:09 am

Re: Possible Scout main jet sizes.

hi are you using a reproduction brass float?
regards jib
Dude, check out that jibhead, he's crazy. Hasn't been sober for 40 years
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panic

Post Fri May 07, 2010 12:02 pm

Re: Possible Scout main jet sizes.

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Last edited by panic on Sun Nov 28, 2010 6:13 pm, edited 1 time in total.
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dirtyss

Posts: 16

Joined: Sat Feb 27, 2010 8:05 am

Post Tue May 11, 2010 2:03 am

Re: Possible Scout main jet sizes.

Panic, how much of the transfer slot should I see with the throttle plate fully closed ? I checked the size of the small transfer hole on the engine side - that is at the standard size. Checked again for leaks - new spindle, bushes and throttle plate - I'm wondering if it could be the new throttle plate not seating fully.

Hey Jib, Not sure if the float is repro or not as it came with the bike, it looks pretty old and battered - tested it for leaks - seems ok, carb does not flood.

Regards
Paul
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panic

Post Tue May 11, 2010 6:08 am

Re: Possible Scout main jet sizes.

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Last edited by panic on Sun Nov 28, 2010 6:13 pm, edited 1 time in total.
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dirtyss

Posts: 16

Joined: Sat Feb 27, 2010 8:05 am

Post Mon May 31, 2010 2:51 am

Re: Possible Scout main jet sizes.

Ok, the good news. :D
Using Cottens leak detection set up I found the leak.
The bad news. :(
The front cylinder inlet nipple was loose. Complete new can of worms - cannot get the nut off (I may cut it depending on availabilty of nut over here) - then there is the re-sealing and locking of the nipple..........
I'll do a search on this issue, and probably start a new thread on this, seeing as I'm a few miles from my original jet thread question.
Regards
Paul

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